RIPEMD-160 collision, first 48 bits (λ = 24)

The distinct eight-byte inputs in collision.json have identical first six digest bytes. Hex strings represent decoded bytes, not literal UTF-8 text.

Field	Value
inputA	0x19bef10000000000
inputB	0x1022730100000000
RIPEMD-160(inputA)	902e5fc86be47b1e2a17de2aab65d4e765623a05
RIPEMD-160(inputB)	902e5fc86be4a99253faddc650510cb85e77233d
Shared 48-bit MSB prefix	902e5fc86be4

Evidence and method

These values were computed locally, not inferred from published claims. The delivered artifacts/search.c enumerates eight-byte little-endian counters and stores candidates in an open-addressed table. Every candidate match compares the first six RIPEMD-160 digest bytes. It found counters 15,842,841 and 24,322,576 after searching 24,322,577 distinct inputs, starting at zero.

The delivered artifacts/verify.py reads the actual JSON, checks its exact keys, algorithm, lambda and distinct decoded inputs, recomputes both full digests using Python hashlib, compares them with OpenSSL CLI results, and asserts equality of the first six bytes. Running it completed successfully and printed "verified": true with the hashes above. OpenSSL on this machine reports version 3.0.13.

Reproduce

From the repository root, verify the delivered result without repeating the search:

python3 artifacts/verify.py

To repeat the deterministic search on Linux with GCC and OpenSSL 3's system libcrypto.so.3 installed:

mkdir -p test/scratch
gcc -O3 artifacts/search.c -Wl,-l:libcrypto.so.3 -o test/scratch/search
test/scratch/search > test/scratch/reproduced.json
cmp collision.json test/scratch/reproduced.json

The search uses a 256 MiB table. No network, secrets or external data are used. No packages were installed. System GCC, Python and OpenSSL are runtime prerequisites, not vendored dependencies.

Limits

The full 160-bit hashes differ: the demonstrated collision applies only to the requested first 48 bits. Python and the CLI provide separate checking paths but may share the same underlying OpenSSL implementation; this is a local self-check, not an independent cryptographic implementation or SIMD attestation. SIMD verification has not been run here. There are no remaining unknowns about the locally computed prefix equality.